Pointing devices, such as computer mice or trackballs, are utilized for inputting data into and interfacing with personal computers and workstations. Such devices allow rapid relocation of a cursor on a monitor, and are useful in many text, database and graphical programs. A user controls the cursor, for example, by moving the mouse over a surface to move the cursor in a direction and over distance proportional to the movement of the mouse. Alternatively, movement of the hand over a stationary device may be used for the same purpose.
Computer mice come in both optical and mechanical versions. Mechanical mice typically use a rotating ball to detect motion, and a pair of shaft encoders in contact with the ball to produce a digital signal used by the computer to move the cursor. One problem with mechanical mice is that they are prone to inaccuracy and malfunction after sustained use due to dirt accumulation, and such. In addition, the movement and resultant wear of the mechanical elements, particularly the shaft encoders, necessarily limit the useful life of the device.
One solution to the above-discussed with mechanical mice problems has been the development of optical mice. Optical mice have become very popular because they are more robust and may provide a better pointing accuracy.
One approach used for optical mice relies on a light emitting diode (LED) illuminating a surface at or near grazing incidence, a two-dimensional CMOS (complementary metal-oxide-semiconductor) detector which captures the resultant images, and software that correlates successive images to determine the direction, distance and speed the mouse has been moved. This technology typically provides high accuracy but suffers from a complex design and relatively high image processing requirements. In addition, the optical efficiency is low due to the grazing incidence of the illumination.
Another approach uses one-dimensional arrays of photo-sensors or detectors, such as photodiodes. Successive images of the surface are captured by imaging optics, translated onto the photodiodes, and compared to detect movement of the mouse. The photodiodes may be directly wired in groups to facilitate motion detection. This reduces the photodiode requirements, and enables rapid analog processing. An example of one such a mouse is disclosed in U.S. Pat. No. 5,907,152 to Dandliker et al. The mouse disclosed in Dandliker et al. also differs from the standard technology in that it uses a coherent light source, such as a laser. Light from a coherent source scattered off of a rough surface generates a random intensity distribution of light known as speckle.
Devices using the above-mentioned prior approaches typically have various disadvantages and drawbacks. For example, they are generally multi-component devices which are manufactured using separate components. The separate components typically include a light source, an illumination beam deviator, an integrated sensor array and circuitry, and a collection lens or other imaging optics.
The present application discloses a novel design for an optical positioning device. The disclosed design provides advantages over prior art devices in regards to reduced complexity, fewer components, and ease of manufacturing, while maintaining sufficiently accurate tracking of the device movement.